MINERALS How to identify a mineral by its properties Wolf Island Science

TODAY YOU WILL LEARN The definition of a mineral Properties that are important in identification. Wolf Island Science

YES OR NO Is this a mineral? Wolf Island Science

Baker 7th grade science

WHAT IS A MINERAL? A mineral is a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition Wolf Island Science

A MINERAL’S APPEARANCE HELPS IDENTIFY IT. In order to identify a mineral, you need to observe it properties – characteristics that help identify it. There are 5 main properties that we use to identify. There are many minor properties that can also help id a mineral. Baker 7th grade science

MINERAL PROPERTY #1 COLOR Color is the first thing someone notices when they view a mineral. Color is also one of the big reasons that attract people to minerals. Generally speaking, color is not a good property to be used in the identification of minerals. It is usually the first property to confuse a novice collector into making an incorrect identification. Many minerals have different colors and some minerals' colors are identical to other minerals' colors. Baker 7th grade science

MINERAL PROPERTY #2 STREAK Streak is closely related to color, but is a different property because the color of the mineral may be different than the color of the streak. color Streak is actually the color of the powder of a mineral. It is called streak because the proper way to test for streak is to rub a mineral across a tile of white unglazed porcelain and to examine the color of the "streak" left behind. Baker 7th grade science

MINERAL PROPERTY 1 & 2 COLOR & STREAK Pyrite (known as "Fool's Gold") is always brassy yellow when found in crystals, even broken crystals, of any size; but when powdered, produces a black streak. Gold's streak, by the way, is yellow! Hematite's streak is blood-red Galena's streak is lead gray Baker 7th grade science

MINERAL PROPERTY # 3 LUSTER A mineral’s luster is the way in which light reflects from the surface. The two major types of luster are metallic & nonmetallic. Baker 7th grade science

MINERAL PROPERTY # 3 LUSTER Some other ways to describe luster are Dull - just a non-reflective surface of any kind Earthy - the look of dirt or dried mud Fibrous - the look of fibers Greasy - the look of grease Gumdrop - the look a sucked on hard candy Metallic - the look of metals Pearly - the look of a pearl Pitchy - the look of tar Resinous - the look of resins such as dried glue or chewing gum Silky - the look of silk, similar to fibrous but more compact Submetallic - a poor metallic luster, opaque but reflecting little light Vitreous - the most common luster, it simply means the look of glass Waxy - the look of wax Baker 7th grade science

QUICK CHECK Get out your quizdom and quickly answer the following: What is the first thing someone notices about a mineral? What do we call the color of the powdered mineral? Which is more reliable: streak or color? Baker 7th grade science

WHAT IS THE FIRST THING SOMEONE NOTICES ABOUT A MINERAL? A)Color B)Luster C)Streak Baker 7th grade science

WHAT DO WE CALL THE COLOR OF THE POWDERED MINERAL? A)Color B)Luster C)Streak Baker 7th grade science

WHICH IS MORE RELIABLE: STREAK OR COLOR? A)Streak B)Color Baker 7th grade science

MINERAL PROPERTY # 4 HOW A MINERAL BREAKS When a mineral breaks it does so either by fracturing or by cleaving. fracturing Cleavage is the tendency of a mineral to break along flat surfaces. Crystal cleavage is a smooth break producing what appears to be a flat crystal face. Fracture is the tendency of a mineral to break into irregular pieces. Baker 7th grade science

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MINERAL PROPERTY #5 HARDNESS A mineral’s hardness is its resistance to being scratched. A scale known as the Moh’s scale is often use Wolf Island Science

Baker 7th grade science

MOHS SCALE Wolf Island Science RatingType mineral What it can be scratched by… 1TalcBaby powder 2Gypsumfingernail 3Calcitebronze coin 4Fluoriteiron nail 5Apatiteglass 6Feldsparpenknife blade 7Quartzsteel knife 8Topazsandpaper 9Corundum 10Diamond

MINERAL PROPERTY #6 DENSITY Each mineral has a specific density. Density is the mass of a given space or in scientific terms the mass per unit of volume. For example, if you have two minerals of the same size one might be heavier than the other. The galena will be three times heavier than the same size of quartz. Wolf Island Science

MINERAL PROPERTY #6 DENSITY Geologists measure density by the following: First they use a balance to determine the mass of a sample. Second, they place the mineral in water to see how much water it displaces. The volume of displace water = the volume of the sample Third they use the following formula: Density = Mass/Volume Wolf Island Science

BRAIN CHECK Get out your whiteboard and quickly answer the following: If you break a mineral and it breaks into cubes, is it fracture or cleavage? Why? If you break a mineral with a hammer and it falls apart into a million different pieces, is it fracture or cleavage? Why? Name three things you can scratch talc with. What is the formula for density? Wolf Island Science

SOME MINERALS HAVE SPECIFIC PROPERTIES - EXTRAS Fluorescence: some minerals glow when exposed to ultraviolet light Magnetic: Some minerals are attracted to magnets Acid: Some minerals react with acid by bubbling Wolf Island Science

S S treak Powdered Color L L uster How shiny C C leavage Breaks in sheets or blocks D D ensity How much mass in a given volume F F racture Just crumbles & breaks H H ardness Can be scratched by E E xtras – density, magnetism, reactions Wolf Island Science